The present invention relates generally to grinding apparatus and more particularly to apparatus using abrasive grinding belts.
Abrasive belt grinding apparatus are used in a variety of applications and can be used for flat grinding procedures or contour grinding procedures. In many grinding applications such as for example in knifemaking and other general grinding and polishing operations relative complicated contours are often required necessitating the use of a relatively large number of different tools. Such tools can be in the form of contact wheels of different diameters over which the abrasive belt can pass. Most currently known apparatus are adapted to only support one tool at a time. As such, it is necessary to continually change tools where complicated contours are being formed This is not only time consuming but costly.
In U.S. Pat. No. 4,434,584 there is described turret belt grinder which is adapted to support different size contact wheels in a support frame with an abrasive belt extending over the wheels. The frame is adapted to be rotated relative to mounting structure and is adapted for rotation relative thereto so that each wheel can be rotated to a common work station. The abrasive belt is driven by a V-belt which transmits power from a centrally located motor shaft to a contact drive wheel. This device suffers from several drawbacks. For example, in order to access internal square corners the number of tools which can be carried by the support frame is limited to three. In addition the drive arrangement is complicated and limits the functionality of the device.
Another problem associated with abrasive belt grinding apparatus is control of the belt during operation Belt tracking devices are known but are usually relatively complicated and can be unreliable.
It is therefore an object of the present invention to provide apparatus which alleviates one or more of the aforementioned problems.
According to one aspect of the present invention there is provided a tool support device for use in a belt grinding apparatus, the apparatus including, a drive motor, a drive shaft, and an abrasive belt arranged to be driven by the drive motor. The tool support device includes a primary carriage operatively connectable to a support structure, the primary carriage including a plurality of mounting zones thereon, each mounting zone being adapted to receive a primary working tool assembly, one or more of the primary tool assemblies including a secondary carriage operatively mounted to the primary carriage at one or respective ones of the mounting zones, the primary carriage being mounted for rotary movement so that it can adopt a plurality of working positions, wherein in each working position one of the primary working tools can be selectively disposed at a work station in an operative position, the secondary carriage having a plurality of additional working tools thereon, the secondary carnage being adapted for rotary movement relative to the primary carriage so that one of the additional working tools can be disposed in an operative position when at the work station.
The apparatus may be arranged so that there is a single work station or multiple work stations. When in use the abrasive belt is adapted to be entrained around at least some of the primary tool assemblies.
In one preferred form, the primary carriage may include three mounting zones, each of the zones being adapted to receive a respective primary tool assembly. Two of the primary tool assemblies may be in the form of contact wheels of different diameter. The additional working tools on the or each secondary carriage may also be in the form of contact wheels which are of different diameter to the first mentioned contact wheels. Desirably, because there are only three mounting zones, this permits tools in each zone to be capable of grinding internal radiuses in square corners.
In one preferred embodiment the primary carriage may include a plate like body mounted to a support structure for rotation about an axis of rotation. Preferably, the primary carriage is mounted to the housing of the motor of the grinding apparatus.
Preferably, the plate-like body of the carriage is generally triangular in shape with the mounting zones being disposed in the general region of the three apexes of the triangular shaped plate. Preferably, the angle of the plate like body at each of the apexes is less than 90xc2x0.
In a preferred form of the invention when in the assembled position, the drive shaft of the motor is operatively connected to one of the contact wheels so as to generally coaxial therewith, this contact wheel causing movement of the abrasive belt over the other working tool assemblies. Preferably, rotation of the primary carriage is about the axis of the drive shaft.
The device may further include a platen operatively connected to the primary carriage body in a position between the mounting zones. The platen is arranged adjacent the abrasive belt when in use for use in flat grinding operations.
The secondary carriage may in one form include a carriage body which is mounted for rotation on the primary carriage at one or two of the mounting zones so that it can adopt a plurality of operative positions. The secondary carriage body may include a hub section and three sets of generally radially extending mounting arms each set of mounting arms being adapted to support a respective contact wheel. Locking means which may be in the form of a releasable locking pin may be provided to lock the secondary carriage relative to the primary carriage in a selected one of its operating positions.
The device may further include a locking assembly for releasably holding the primary support carriage in a selected one of its operating positions. In one form, the locking assembly may include a mounting plate having a plurality of locating recesses therein, the mounting plate being attached to the housing of the motor. A detent is operatively connected to the carriage through an adjustment arm, the detent being adapted to cooperate with the locating recesses to hold the carriage relative to the motor in one of a selected number of operating positions. A spring may be arranged to urge the detent into engagement with a selected one of the locating recesses.
Preferably, at least some of the tool assemblies are operatively mounted to the primary carnage by means of adjustable generally conical shaped mounting pivots. By this arrangement any wear between the parts can be adjusted for. This feature is particular valuable in provided for accurate tracking of the belt over the tool assemblies. Furthermore, low friction material such as Teflon preferably in the form of a layer may be provided between the primary carriage and the tool assembly.
The apparatus may further include a belt tensioning device which in one form includes a lever and slot assembly which causes movement of tool assembly relative to the support carriage to thereby relieve or apply a tension to the belt.
One or more safety shields may be provided at the mounting zones. In a preferred form the or each safety shield may include a main body mounted to the primary carriage for pivotal movement relative thereto between a retracted position and an in use position The shield further includes a cover portion which in the in use position overlies the belt.
According to another aspect of the present invention there is provided a tracking adjustment mechanism for correcting the tracking of a belt on a belt drive. The mechanism including an axle assembly operatively mounted to a support carriage, the assembly including an axle upon which a contact wheel is mounted for rotation, the axle includes opposed end bearings one of which provides for at least limited pivotal movement of the axle. Preferably, the limited pivotal movement in is the form of limited universal movement. The bearing may include an adjustable ball and socket assembly. The other bearing may include an eccentric thereon which is operable by a lever so that rotation of the eccentric causes pivotal movement of the axle in the other bearing thereby adjusting the position of the axle relative to the support carriage. This tracking adjustment mechanism may be used in the tool support device according to the first mentioned aspect of the invention.
Preferably, the tracking mechanism includes an axle assembly which is mountable to the primary carriage via mounting brackets, each having a bearing mounting therein. One of the bearing mountings may be in the form of a curved mounting surface in the mounting bracket which is complementary in shape to a portion of a sphere. The other bearing mounting may be in the form of a circular aperture in mounting bracket.
The axle assembly may further include an axle having end bearings, these end bearings being receivable within respective bearing mountings on the mounting brackets. The end bearing may be in the form of a at least part hemispherical ball which in the assembled position is adapted to be disposed within the curved mounting surface of the bearing mounting. The bearing may be in the form of a head of a screw element which is securable to axle. An adjustment nut enables the bearing to be tightly received within the bearing mounting socket and enables subsequent adjustment if wearing occurs.
The other bearing may be in the form of a collar which is eccentrically disposed with respect to the longitudinal axis of the axle. The collar is receivable within bearing mounting and can be rotated therein by means of actuating lever. A spring which may be in the form of a disc spring ensures that the various parts are held in a tight relationship with respect to one another.
It will be appreciated that the apparatus of the present invention can provide up to seven different tools with each tool being able to access an internal square corner of the component being worked.